This is a competitive renewal application for T32 DK07260, entitled "Training Grant in Diabetes and Metabolism," currently in its 25th year. This program provides multi-disciplinary training in diabetes research for predoctoral students and postdoctoral fellows (MD and/or PhD) at the Research Division of the Joslin Diabetes Center in Boston. Its rationale is: 1) that diabetes is currently a devastating world health problem from both a human and economic standpoint; 2) that the Joslin, given its rich history of diabetes research and its current breadth and excellence, is a unique environment for training the corps of researchers required to solve this problem; and 3) that the Joslin can already demonstrate an impressive research training record. The Program Director is Dr. Diane Mathis and Co-Director Dr. George King, who are supported by an Executive Committee. The postdoctoral training faculty consists of thirty-eight investigators at the Joslin Diabetes Center; the predoctoral faculty is primarily the subset holding appointments in the Division of Medical Sciences at Harvard Medical School. The individual Preceptors provide a mentor-based research experience that ranges from the most basic through the preclinical to the clinical, exploiting approaches that span the computational, biophysical, biochemical, molecular biological, cellular biological and organismic. Areas of focus include insulin signaling, intermediary metabolism, vascular cell biology, islet cell physiology, obesity, immunology, epidemiology, genetics, and mental health. Training is enhanced by Joslin's NIH-supported Diabetes and Endocrinology Research Center (DERC) and its strong ties with Harvard Medical School, both of which provide access to state-of-the-art technologies as well as to a core of lectures/seminars by leading scientists from around the world. The program currently supports five postdoctoral fellows and two predoctoral students; here support for a third predoctoral position is requested. This augmentation is justified by the increased vigor of Joslin's predoctoral component, with the recruitment of new investigators active in graduate education and the scientific maturation of others, signaled by a doubling of the number of predoctoral applications in 1999-2000 and tripling in 2000-2001. Support for two short-term predoctoral fellows is also requested, reflecting the strength of and interest in Joslin's Summer Research Training Program.